Ida M. Cox (Prather; February 26, 1888 or 1896 – November 10, 1967) was an American singer and vaudeville performer, best known for her blues performances and recordings. She was billed as “The Uncrowned Queen of the Blues”.

Cox was born Ida M. Prather, the daughter of Lamax and Susie (née Knight) Prather in Toccoa, then Habersham County, Georgia, and grew up in Cedartown, Polk County, Georgia. Many sources give her birth date as February 26, 1896, but the researchers Bob Eagle and Eric LeBlanc have suggested she was born in 1888, and noted other evidence suggesting 1894.